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Subject: Re: [PATCH 01/11] arch: Export cpu_logical_map to modules
To:     Rob Herring <robh+dt@kernel.org>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Ray Jui <rjui@broadcom.com>,
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        Catalin Marinas <catalin.marinas@arm.com>,
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        Rich Felker <dalias@libc.org>,
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        Andrew Morton <akpm@linux-foundation.org>,
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References: <20210924170546.805663-1-f.fainelli@gmail.com>
 <20210924170546.805663-2-f.fainelli@gmail.com>
 <CAL_JsqLp0o9CpG=ej3HsnDO-bG02CF4a55sYTOvxMR3rMyboqg@mail.gmail.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <69444f17-91a7-69cc-14f8-7501443064ec@gmail.com>
Date:   Mon, 27 Sep 2021 12:43:34 -0700
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On 9/27/21 12:32 PM, Rob Herring wrote:
> On Fri, Sep 24, 2021 at 12:06 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>>
>> In order to allow drivers/irqchip/irq-bcm7038-l1.c to be built as a
>> module and usable in GKI, export cpu_logical_map or __cpu_logical_map
>> towards the modules.
> 
> This is the usage:
> 
> #ifdef CONFIG_SMP
>         cpu = intc->cpus[cpu_logical_map(smp_processor_id())];
> #else
>         cpu = intc->cpus[0];
> #endif
> 
> This is totally broken! cpu_logical_map() takes the logical cpu
> number, 0-N, and returns the MPIDR which you then use as an array
> index.

There is no MPIDR on MIPS, which is where this code is being primarily
used as-is. On ARM/ARM64 the driver is used as a second level interrupt
controller with only a single "bank" of registers as opposed to one
per-CPU, meaning that we would always use intc->cpus[0] because you
cannot change the interrupt affinity of a second level interrupt
controller AFAICT. Maybe the above deserves to be made CONFIG_SMP &&
CONFIG_MIPS somehow.
-- 
Florian